Which of the following are used as carbon dioxide absorbers?

• A. Soda lime
• B. Barium sulfate
• C. Barium hydroxide
• D. A and C

Answer: (D)

In closed-circuit breathing systems, CO2 is removed by chemical reactions with alkaline absorbers. Soda lime is a common absorber that reacts with carbon dioxide to form calcium carbonate and water, effectively scrubbing CO2 from the gas. Barium hydroxide works similarly in Baralyme-style absorbers by reacting with CO2 to form barium carbonate and water. Barium sulfate, on the other hand, is chemically inert with respect to CO2 and is used as a filler or radiopaque agent, not a CO2 absorber. Because both soda lime and barium hydroxide absorb CO2, the best answer is the one that lists both.